Answer this question truthfully
### Question: What causes Erythema nodosum?
### Response: In about half of cases, the exact cause of erythema nodosum is unknown. Some cases may be associated with the following:
Infections. Some of the more common ones are:
Streptococcus (most common) Cat scratch disease Chlamydia Coccidioidomycosis Hepatitis B Histoplasmosis Leptospirosis Mononucleosis (EBV) Mycobacteria Mycoplasma Psittacosis Syphilis Tuberculosis Tularemia Yersinia
Pregnancy Sensitivity to certain medications, including:
Amoxicillin and other penicillins Sulfonamides Sulfones Oral contraceptives Other antibiotics Progestin
Other associated disorders include leukemia, lymphoma, sarcoidosis, rheumatic fever, Bechet's disease, and ulcerative colitis.